Autumn temperatures in the Arctic are at record levels, the Arctic Ocean is getting warmer and less salty as sea ice melts and reindeer herds appear to be declining, researchers reported Thursday.
"Obviously, the planet is interconnected, so what happens in the Arctic does matter" to the rest of the world, Jackie Richter-Menge of the Cold Regions Research and Engineering Laboratory in Hanover, N.H., said in releasing the third annual Arctic Report Card.
The report, compiled by 46 scientists from 10 countries, looks at a variety of conditions in the Arctic.
The region has long been expected to be among the first areas to show impacts from global warming, which the Intergovernmental Panel on Climate Change says is largely a result of human activities adding carbon dioxide and other gases to the atmosphere.
"Changes in the Arctic show a domino effect from multiple causes more clearly than in other regions," said James Overland, an oceanographer at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle. "It's a sensitive system and often reflects changes in relatively fast and dramatic ways."
For example, autumn air temperatures in the Arctic are at a record 9 degrees Fahrenheit (5 Celsius) above normal.
The report noted that 2007 was the warmest year on record the Arctic, leading to a record loss of sea ice. This year's sea ice melt was second only to 2007.
Rising temperatures help melt the ice, which in turn allows more solar heating of the ocean. That warming of the air and ocean affects land and marine life, and reduces the amount of winter sea ice that lasts into the following summer.
The study also noted a warming trend on Arctic land and increase in greenness as shrubs move north into areas that were formerly permafrost.
While the warming continues, the rate in this century is less than in the 1990s due to natural variability, the researchers said.
In addition to global warming there are natural cycles of warming and cooling, and a warm cycle in the 1990s added to the temperature rise. Now with a cooler cycles in some areas the rise in temperatures has slowed, but Overland said he expects that it will speed up again when the next natural warming cycle comes around.
Asked if an increase in radiation from the sun was having an effect on the Earth's climate, Jason Box of the Byrd Polar Research Center in Columbus, Ohio, said while it's important, increased solar output only accounts for about 10 percent of global warming.
"You can't use solar to say that greenhouse gases are not a major factor," Overland added.
Other findings from the report include:
— The Arctic Ocean continued to warm and freshen due to ice melt. This was accompanied by an "unprecedented" rate of sea level rise of nearly 0.1 inch per year.
— Warming has continued around Greenland in 2007 resulting in a record amount of ice melt. The Greenland ice sheet lost 24 cubic miles of ice, making it the largest single contributor to global sea level rise.
— Reindeer herds that had been increasing since the 1970s are now showing signs of leveling off or beginning to decline.
— Goose populations are increasing as they expand their range within the Arctic.
— Data on marine mammals is limited but they seem to have mixed trends. They are adapted to life in a region that is at least seasonally ice-covered.
There is concern about the small numbers of polar bears in some regions, the status of many walrus groups is unknown, some whales are increasing and others declining.
"This is a very complicated system and we are still working diligently to sort out its mysteries," said Richter-Menge.
In addition to Richter-Menge, Overland and Box, lead authors of the report included Michael Simpkin of NOAA, Silver Spring, Md. and Vladimir E. Romanovsky of the Geophysical Institute, Fairbanks, Alaska.